Name
Class
Date
Skills Worksheet
Directed Reading B
Section: Chemical Formulas and Equations
CHEMICAL FORMULAS
1. All known substances are formed from about
100
elements.
2. A combination of chemical symbols and numbers that represents a
substance is called a(n)
chemical formula
.
3. What does a chemical formula show?
A chemical formula shows how many atoms
of each kind of element are present in a molecule.
a.
______
4. The subscript in the chemical formula H2O tells you there are two
a. atoms of hydrogen in the molecule.
b. electrons on the hydrogen atom in the molecule.
c. elements in the molecule.
d. atoms of oxygen in the molecule.
a. O2
______
5. What is the chemical formula for oxygen?
a. O2
c. H2O
b. C6H12O6
d. Ca(NO3)2
c.
H2O
______
6. What is the chemical formula for water?
a. O2
c. H2O
b. C6H12O6
d. Ca(NO3)2
b. C6H12O6
______
7. What is the chemical formula for glucose?
a. O2
c. H2O
b. C6H12O6
d. Ca(NO3)2
8. Simple covalent compounds are usually composed of two
nonmetals, like H2O, hydrogen and oxygen are nonmetals
.
9. The formula for dinitrogen monoxide is
10. The formula for carbon dioxide is
CO2
11. Ionic compounds are composed of a(n)
nonmetal
N2O
.
.
metal
and a(n)
.
12. The overall charge of an ionic compound is
zero net charge
.
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Holt California Physical Science
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103
Chemical Reactions
Name
Class
Date
Directed Reading B continued
Write the formula for each of the following ionic compounds.
NaCl
13. sodium chloride ______________________________________________________
MgCl2
14. magnesium chloride __________________________________________________
CHEMICAL EQUATIONS
15. What do musical notations and chemical equations have in common?
Musical notation uses symbols to represent
quantities of time, like half note = 4 eighth notes
In chemical equations, symbols (numbers)
tells us the quantities of atoms to use.
16. When chemical symbols and formulas are used to describe a
chemical reaction, it is called a(n)
Chemical equation
.
17. A substance that forms in a chemical reaction is called
a(n)
products
.
18. A substance or molecule that participates in a chemical reaction is called
a(n)
reactants
.
19. When carbon reacts with oxygen to form carbon dioxide, carbon dioxide is
the
product
.
20. What will happen if the wrong chemical symbol or formula is used in a
chemical equation?
If the recipe (chemical equation) says the wrong ingredient (reactant)
there could be a wrong explosive product.
21. In a chemical reaction,
atoms
are never gained or lost.
22. Antoine Lavoisier’s work led to the law of conservation of mass
.
23. What does the law of conservation of mass state?
The law of conservation of mass states that mass is neither created
nor destroyed in chemical and physical changes.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt California Physical Science
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104
Chemical Reactions
Name
Class
Date
Directed Reading B continued
24. A chemical equation must show the same numbers and kinds of
atoms
on both sides of the arrow.
25. The number placed in front of a chemical symbol or formula is called
a(n)
coefficient
.
26. How many oxygen atoms are contained in the formula 2H2O?
2 Oxygen atoms
27. When you balance an equation, only
not
subscripts
coefficients
are changed,
.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Holt California Physical Science
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105
Chemical Reactions
Name
Class
Date
Skills Worksheet
Vocabulary and Section Summary B
Forming New Substances
VOCABULARY
After you finish reading the section, try this puzzle! Fill in the blanks with the
correct terms. Then, find the words in the word search puzzle below. Words may
be hidden horizontally, vertically, backward, or diagonally.
1. In
endothermic
reactions, energy is taken in.
reaction
2. A chemical
is the process by which one or more
substances undergo change to produce one or more new substances with
different properties.
energy
3. The law of conservation of
states that
energy cannot be created or destroyed.
4. In
exothermic
reactions, energy is released.
5. A solid that is produced as a result of a chemical reaction in solution is
precipitate
a(n)
.
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Holt California Physical Science
15
106
Chemical Reactions